1. Field of the Invention
The present invention relates to a telephone set which responds to a plurality of different call signals supplied thereto via a single telephone line.
2. Related Art Statement
There is known a telephone company which offers the service of allotting a plurality of different call numbers to a single telephone line according to a common numbering rule employed thereby.
Subscribers of the telephone company can enjoy this service by using a telephone set or a facsimile machine in relation with each of the different own call numbers. In this case, more telephone sets or facsimile machines may be used with less telephone lines. Otherwise, the subscribers can enjoy the service by using a telephone and facsimile (T/F) apparatus which possesses both the telephone and facsimile functions and has means for automatically switching the T/F apparatus between those two functions. In the latter case, one of the different own call numbers may exclusively be used in relation the telephone function and another of the own call numbers, or the other own call number, may exclusively be used in relation with the facsimile function. An example of the T/F apparatus is disclosed in Japanese Patent Application laid open under Publication No. 4-48855.
The identification of each one of the different own call numbers allotted to the single telephone line, from the other own call numbers, is carried out by supplying, to the single telephone line, different call signals corresponding to the different call numbers, respectively. For example, a basic call signal and a modified call signal obtained by adding a different signal to the basic call signal may be employed to this end. Otherwise, different call signals having different signal patterns may be used.
There is known the "distinctive ringing" service or "dial-in" service wherein different call numbers are identified by different call signals having different signal patterns, respectively. In the distinctive ringing service, the signal pattern of each call signal supplied via a single telephone line to a telephone set is directly utilized by the called telephone set to ring, i.e., produce a calling sound. That is, the ringing device of the telephone set being called produces a calling sound having a sound pattern corresponding to the signal pattern of the call signal supplied thereto. Thus, different calling sounds are produced by a single telephone set in response to different call signals, respectively. The user of the telephone set can identify which call number is being used to call the telephone set, by hearing the sound pattern of the calling sound being produced by the ringing device. According to the distinctive ringing service, a single telephone set functions as if a plurality of telephone sets were used.
For example, in the case where three call numbers are given to a single telephone line, a first and a second one of the three call numbers may be used in relation with the telephone function of a T/F apparatus and the third call number may be used in relation with the facsimile function of the T/F apparatus. If the T/F apparatus is called using the third call number, the facsimile function of the T/F apparatus may automatically receive image information from the calling facsimile machine. If the T/F apparatus is called using the first or second call number, the ringing device of the T/F apparatus produces a calling sound having a sound pattern corresponding to the signal pattern of a supplied call signal identifying the first or second call number. In this particular case, the user of the T/F apparatus may make it a rule that different persons deal with different telephone calls having different calling sounds, respectively, exclusively from each other.
In the above case, it is assumed that the three call numbers allotted to the single telephone line are the number, 1111, for the facsimile function of the T/F apparatus and the numbers, 2222 and 3333, for the telephone function of the same and that the user makes it a rule that Mr. "A" and Mr. "B" share the facsimile number 1111, Mr. "A" exclusively uses the telephone number 2222 and Mr. "B" exclusively uses the telephone number 3333. Mr. "A" lets people know that he uses the number 1111 for the facsimile function and the number 2222 for the telephone function, and similarly Mr. B lets people know that he uses the number 1111 for the facsimile function and the number 3333 for the telephone function. When the T/F apparatus is called using the facsimile number 1111, the facsimile function of the apparatus may automatically receive image information from the calling facsimile machine. When the telephone function of the T/F apparatus is called using one of the two telephone numbers 2222 or 3333, the ringing device of the T/F apparatus produces a calling sound having a sound pattern in accordance with the signal pattern of a supplied call signal identifying the used telephone number 2222 or 3333. Since the respective sound patterns of the calling sounds corresponding to the two telephone numbers are different from each other, Mr. "A" and Mr. "B" can identify who is being called using the corresponding telephone number 2222 or 3333, by hearing the sound pattern of the calling sound being produced by the ringing device.
However, the above-described T/F apparatus suffers from the problem that if Mr. "A" is not available when the T/F apparatus is called using his telephone number 2222, Mr. "B" would have to take the telephone call. Otherwise, if nobody is available, the T/F apparatus would have to be placed in an answering-telephone mode. In the answering telephone mode, however, the T/F apparatus responds in the only and same manner, e.g., transmits the only and same answering message to the calling telephone sets or the calling persons, whichever telephone number 2222 or 3333 may be used to call the T/A apparatus. In those events, therefore, the T/F apparatus functions as if the apparatus had the only and same telephone number in spite of actually having two or more telephone numbers allotted thereto by the telephone company.
U.S. Pat. No. 5,200,992 discloses a facsimile machine which has an outside-line call number allotted thereto according to a first or "public" numbering rule employed by a telephone company, and an extension-line call number allotted thereto according to a second or "private" numbering rule employed by the user of the facsimile machine and other facsimile machines to which the first facsimile machine in question is connected via the extension lines. When the disclosed facsimile machine is called using the outside-line call number by an outside facsimile machine, the called machine transmits the outside-line call number to the calling machine so as to inform that the called machine is receiving image information from the calling machine. Similarly, when the disclosed machine is called using the extension-line call number by another facsimile machine of the user, the called machine transmits the extension-line call number to the calling machine for the same purpose.
However, the above-identified facsimile machine cannot function as if the machine had two or more outside-line call numbers, or two or more extension-line call numbers. When the prior facsimile machine is called via the outside lines, the only and same outside-line call number can be used. Similarly, when the prior facsimile machine is called via the extension lines, the only and same extension-line call number can be used.